Rechargeable batteries are widely used in many products, such as notebooks, tablets, mobile phones, and even large electric vehicles. Generally, rechargeable batteries are composed of a number of rechargeable battery cells linked in series or parallel with the same spec to fulfill a certain power supply. Since each rechargeable battery cell may have unique physical conditions, such as power capacity, when many rechargeable battery cells linked together to work (charge or discharge), difference between two rechargeable battery cells will cause battery unbalance. The battery unbalance situation can further lead to shortening of rechargeable battery life. Therefore, Battery Management Systems (BMS) are used to monitor conditions of rechargeable battery cells and provide actions to treat battery unbalance situation.
It is sure that functions of a BMS are not limited to those mentioned above. With increasing quantity of rechargeable battery cells used in a rechargeable battery, design of the BMS becomes complex. If one BMS can not work to fulfill the purpose of management of all rechargeable battery cells, a number of BMS' must linked to co-work or a BMS has to work with the aid of several sub-units. A popular concept of BMS operation is to apply master-slave control communication. A solution is provided in U.S. Pat. No. 8,237,405. '405 discloses a battery management system which can include a rechargeable battery having a number of rechargeable battery cells, a number of devices coupled to the rechargeable battery, and a control unit coupled to a first device of the devices. The devices can assess the statuses of the rechargeable battery cells. The control unit can communicate with a destination device of the devices via a default path and can communicate with the destination device via a backup path if an undesirable condition occurs in the default path.
A feature of the '405 is the communicating method applied in the battery management system. The communicating method uses master-slave control and can make the battery management system extensible to large number of linked battery cells. However, under such architecture, signals communicated is achieved by current and charge transfer. It will cause high power consumption. Meanwhile, '405 is not able to apply to many popular protocols for internal communication.
Therefore, a master-slave control type system of communication which can consume less power and apply to many popular internal communicating protocols is still desired. The system of communication functions well in a BMS.